Controlled crystalline orientation of SrTiO3 thin films grown on Pt(111)/Ti/α-Al2O3(0001) substrates: Effect of growth temperature and Ti layer thickness

SrTiO3 (STO) thin films were grown on Pt(1 1 1)/Ti/alpha-Al2O3(0 0 0 1) substrates by ion beam sputter deposition. Growth temperature was varied between 600 and 750 degrees C, while Ti layer thickness was adjusted from 3 to 36 nm. Experimental results demonstrate that both the crystalline orientation and surface morphology are significantly dependent on change in the growth temperature and Ti layer thickness. From X-ray structural analysis, the STO thin films grown at 600 degrees C are perfectly (1 1 0)-oriented in spite of the change in Ti layer thickness. The STO thin films with a perfect (1 1 1) orientation are achievable at a sufficiently high growth temperature (>= 700 degrees C) and a thin Ti layer (3-6 nm). Each crystalline orientation of STO thin films has a specific in-plane orientation relationship with respect to the Pt(1 1 1) layer. Flat-, rod-, and triangle-shaped grains are clearly observed from atomic force microscopy investigation, which are associated with the (1 1 0)-, (1 0 0)-, and (1 1 1)-oriented grains, respectively. Their grain orientations also show a good correlation with the X-ray structural analysis. The growth mechanism of each crystalline orientation can be described in term of surface diffusion, surface energy anisotropy, electrostatic, and role of TiOx seeds. (C) 2014 Elsevier B.V. All rights reserved.